I. Definitions
As used herein, the phrase “group III-V” refers to a compound semiconductor including at least one group III element and at least one group V element. By way of example, a group III-V semiconductor may take the form of a III-Nitride semiconductor. “III-Nitride”, or “III-N”, refers to a compound semiconductor that includes nitrogen and at least one group III element such as aluminum (Al), gallium (Ga), indium (In), and boron (B), and including but not limited to any of its alloys, such as aluminum gallium nitride (AlxGa(1-x)N), indium gallium nitride (InyGa(1-y)N), aluminum indium gallium nitride (AlxInyGa(1-x-y)N), gallium arsenide phosphide nitride (GaAsaPbN(1-a-b)), aluminum indium gallium arsenide phosphide nitride (AlxInyGa(1-x-y)AsaPbN(1-a-b)), for example. III-Nitride also refers generally to any polarity including but not limited to Ga-polar, N-polar, semi-polar, or non-polar crystal orientations. A III-Nitride material may also include either the Wurtzitic, Zincblende, or mixed polytypes, and may include single-crystal, monocrystalline, polycrystalline, or amorphous structures. Gallium nitride or GaN, as used herein, refers to a III-Nitride compound semiconductor wherein the group III element or elements include some or a substantial amount of gallium, but may also include other group III elements in addition to gallium.
II. Background Art
A III-nitride heterojunction semiconductor device can include a III-nitride heterojunction having a first III-nitride body of one bandgap and a second III-nitride body of another bandgap formed over the first III-nitride body. The composition of the first and second III-nitride bodies are selected to cause the formation of a carrier rich region referred to as a two-dimensional electron gas (2DEG) at or near the III-nitride heterojunction. The 2DEG can serve as a conduction channel between a first power electrode (e.g. a source electrode) and a second power electrode (e.g. a drain electrode).
The III-nitride heterojunction semiconductor device can also include a gate electrode disposed between the first and second power electrodes to selectively interrupt or restore the 2DEG therebetween, whereby the device may be operated as a switch. The gate electrode may be received by a trench that extends through a passivation body. The trench in which the gate electrode is received includes vertical sidewalls that form sharp bottom corners in the gate electrode. This can result in high electric field regions at the bottom corners of the gate electrode, as well as an increase in the overlap between the gate electrode and the 2DEG.